derivatives of carboxylic acid - جامعة تكريت - كلية...
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Derivatives of Carboxylic Acid
acid chloride
carboxylate
nitrile
amide
ester
acid anhydride
Nomenclature of Acid Halides
IUPAC: alkanoic acid → alkanoyl halide
Common: alkanic acid → alkanyl halide
I: 3-aminopropanoyl chloride
c: b-aminopropionyl chloride
I: 4-nitropentanoyl chloride
c: g-nitrovaleryl chloride
I: hexanedioyl chloride
c: adipoyl chloride
Rings: (IUPAC only): ringcarbonyl halide
I: 3-cylcopentenecarbonyl chloride
I: benzenecarbonyl bromide
c: benzoyl bromide
Nomenclature of Acid
Anhydrides
Acid anhydrides are prepared by dehydrating carboxylic acids
acetic anhydride
ethanoic acid ethanoic anhydride
I: benzenecarboxylic anhydride
c: benzoic andhydride I: butanedioic acid
c: succinic acid
I: butanedioic anhydride
c: succinic anhydride
Some unsymmetrical anhydrides
I: cis-butenedioic
anhydride
I: benzoic methanoic anhydride
c: benzoic formic anhydride
I: ethanoic methanoic
anhydride
c: acetic formic anhydride
Nomenclature of Esters Esters occur when carboxylic
acids react with alcohols
I: methyl ethanoate
c: methyl acetate
I: phenyl methanoate
c: phenyl formate
I: t-butyl benzenecarboxylate
c: t-butyl benzoate
I: isobutyl
cyclobutanecarboxylate
c: none
I: cyclobutyl 2-
methylpropanoate c: cyclobutyl a-
methylpropionate
I: dimethyl ethanedioate
c: dimethyl oxalate
Cyclic Esters
Reaction of -OH and -COOH on same molecule
produces a cyclic ester, lactone.
To name, add word lactone to the IUPAC acid name or
replace the -ic acid of common name with -olactone.
4-hydroxy-2-methylpentanoic acid lactone
-methyl- -valerolactone
Amides
Product of the reaction of a carboxylic
acid and ammonia or an amine.
Not basic because the lone pair on
nitrogen is delocalized by resonance.
Classes of Amides
1 amide has one C-N bond (two N-H).
2 amide or N-substituted amide has
two C-N bonds (one N-H).
3 amide or N,N-disubstituted amide
has three C-N bonds (no N-H).
=>
Naming Amides
For 1 amide, drop -ic or -oic acid from
the carboxylic acid name, add -amide.
For 2 and 3 amides, the alkyl groups
bonded to nitrogen are named with N- to
indicate their position.
N-ethyl-N,2-dimethylpropanamide
N-ethyl-N-methylisobutyramide
Cyclic Amides
Reaction of -NH2 and -COOH on same
molecule produces a cyclic amide, lactam.
To name, add word lactam to the IUPAC
acid name or replace the -ic acid of
common name with -olactam.
4-aminopentanoic acid lactam
-valerolactam
Relative Reactivity of Carbonyl Carbons
Nucleophiles (electron donors), like OH-, bond with the sp2 hybridized
carbonyl carbon.
The order of reactivity is shown.
Nitriles
-C≡N can be hydrolyzed to carboxylic
acid, so nitriles are acid derivatives.
Nitrogen is sp hybridized, lone pair tightly
held, so not very basic. (pKb about 24).
Naming Nitriles
For IUPAC names, add -nitrile to the
alkane name.
Common names come from the
carboxylic acid. Replace -ic acid with -
onitrile.
5-bromohexanenitrile
-bromocapronitrile
Cyclohexanecarbonitrile
=>
Acid Halides
More reactive than acids; the halogen
withdraws e- density from carbonyl.
Named by replacing -ic acid with -yl
halide.
benzoyl chloride
3-bromobutanoyl bromide
-bromobutyryl bromide
=>
Acid Anhydrides
Two molecules of acid combine with the loss of
water to form the anhydride.
Anhydrides are more reactive than acids, but
less reactive than acid chlorides.
A carboxylate ion is the leaving group in
nucleophilic acyl substitution reactions.
Naming Anhydrides
The word acid is replaced with anhydride.
For a mixed anhydride, name both acids.
Diacids may form anhydrides if a 5- or 6-
membered ring is the product.
ethanoic anhydride
acetic anhydride 1,2-benzenedicarboxylic anhydride
phthalic anhydride
Multifunctional Compounds
The functional group with the highest
priority determines the parent name.
Acid > ester > amide > nitrile > aldehyde
> ketone > alcohol > amine > alkene >
alkyne.
ethyl o-cyanobenzoate
Boiling Points
Even 3º amides have
strong attractions.
Melting Points
Amides have very high melting points.
Melting points increase with increasing
number of N-H bonds.
m.p. -61ºC m.p. 28ºC m.p. 79ºC
Solubility
Acid chlorides and anhydrides are too reactive to be used with water or alcohol.
Esters, 3º amides, and nitriles are good polar aprotic solvents.
Solvents commonly used in organic reactions:
Ethyl acetate
Dimethylformamide (DMF)
Acetonitrile =>
IR Spectroscopy
1H NMR Spectroscopy
13C NMR Spectroscopy
Interconversion of
Acid Derivatives Nucleophile adds to the carbonyl to form
a tetrahedral intermediate.
Leaving group leaves and C=O
regenerates.
Reactivity
Reactivity decreases as leaving group
becomes more basic.
Interconversion of Derivatives
More reactive
derivatives can be
converted to less
reactive derivatives.
Acid Chloride to Anhydride
Acid or carboxylate ion attacks the C=O.
Tetrahedral intermediate forms.
Chloride ion leaves, C=O is restored, H+
is abstracted.
=>
Acid Chloride to Ester
Alcohol attacks the C=O.
Tetrahedral intermediate forms.
Chloride ion leaves, C=O is restored, H+
is abstracted.
=>
Acid Chloride to Amide
Ammonia yields a 1º amide
A 1º amine yields a 2º amide
A 2º amine yields a 3º amide
Anhydride to Ester
Alcohol attacks one C=O of anhydride.
Tetrahedral intermediate forms.
Carboxylate ion leaves, C=O is restored,
H+ is abstracted.
=>
Anhydride to Amide
Ammonia yields a 1 amide
A 1 amine yields a 2 amide
A 2 amine yields a 3 amide
Ester to Amide
Nucleophile must be NH3 or 1 amine.
Prolonged heating required.
Leaving Groups
A strong base is not usually a leaving
group unless it’s in an exothermic step.
Transesterification
One alkoxy group can be replaced by
another with acid or base catalyst.
Use large excess of preferred alcohol.
Hydrolysis of Acid
Chlorides and Anhydrides Hydrolysis occurs quickly, even in moist
air with no acid or base catalyst.
Reagents must be protected from
moisture.
Acid Hydrolysis of Esters
Reverse of Fischer esterification.
Reaches equilibrium.
Use a large excess of water.
Saponification
Base-catalyzed hydrolysis of ester.
“Saponification” means “soap-making.”
Soaps are made by heating NaOH with a
fat (triester of glycerol) to produce the
sodium salt of a fatty acid - a soap.
One example of a soap is sodium
stearate, Na+ -OOC(CH2)16CH3.
=>
Hydrolysis of Amides
Prolonged heating in 6 M HCl or 40%
aqueous NaOH is required.
Hydrolysis of Nitriles
Under mild conditions, nitriles hydrolyze
to an amide.
Heating with aqueous acid or base will
hydrolyze a nitrile to an acid.
Reduction to Alcohols
Lithium aluminum hydride reduces acids,
acid chlorides, and esters to primary
alcohols.
Reduction to Aldehydes
Acid chlorides will react with a weaker
reducing agent to yield an aldehyde.
Reduction to Amines
Lithium aluminum hydride reduces amides
and nitriles to amines.
Nitriles and 1 amides reduce to 1
amines.
A 2 amide reduces to a 2 amine.
A 3 amide reduces to a 3 amine.
Organometallic Reagents
Grignard reagents and organolithium
reagents add twice to acid chlorides and
esters to give alcohols after protonation.
Grignard Reagents
and Nitriles A Grignard reagent or organolithium
reagent attacks the cyano group to yield
an imine which is hydrolyzed to a ketone.
Acid Chloride Synthesis
Use thionyl chloride, SOCl2, or oxalyl
chloride, (COCl)2.
Other products are gases.
Acid Chloride Reactions (1)
acid
ester
amide
acid anhydride
Acid Chloride Reactions (2)
3° alcohol
ketone
1° alcohol
aldehyde
acylbenzene
Industrial Synthesis
of Acetic Anhydride Four billion pounds/year produced.
Use high heat (750°C) and triethyl
phosphate catalyst to produce ketene.
Lab Synthesis
of Anhydrides React acid chloride with carboxylic acid
or carboxylate ion.
Heat dicarboxylic acids to form cyclic anhydrides.
Anhydride Reactions
Anhydride vs. Acid Chloride
Acetic anhydride is cheaper, gives a better
yield than acetyl chloride.
Use acetic formic anhydride to produce
formate esters and formamides.
Use cyclic anhydrides to produce
a difunctional molecule.
Synthesis of Esters
Reactions of Esters
Lactones
Formation favored for five- and six-
membered rings.
For larger rings, remove water to shift equilibrium
toward products
Synthesis of Amides
Reactions of Amides
acid and amine
amine
1° amine
nitrile
Lactam Formation
Five- and six-membered rings can be
formed by heating - and -amino acids.
Smaller or larger rings do not form readily.
-Lactams
Highly reactive, 4-membered ring.
Found in antibiotics isolated from fungi.
Synthesis of Nitriles
Reactions of Nitriles
Thioesters
More reactive than esters because:
◦ -S-R is a better leaving group than -O-R
◦ Resonance overlap is not as effective.
Carbonic Acid Esters
CO2 in water contains some H2CO3.
Diesters are stable.
Synthesized from phosgene.
Urea and Urethanes
Urea is the diamide of carbonic acid.
Urethanes are esters of a monoamide of
carbonic acid.
Polymers
Polycarbonates are long-chain esters of
carbonic acid.
Polyurethanes are formed when a diol
reacts with a diisocyanate.